Permanent magnet generators of the type having a rotor made up of two relatively movable permanent magnet rotor bodies have been proposed generally to provide for voltage regulation in response to changes in loading on the generator. They have also been employed for regulating voltage to compensate for changes in the rate of rotor rotation.
Examples of such proposals can be found in U.S. Pat. Nos. 3,233,133 issued Feb. 1, 1966 to Kober; 3,713,015 issued Jan. 23, 1973 to Frister; and 4,305,031 issued Dec. 8, 1981 to Wharton. Typical of these constructions is an arrangement wherein one of the permanent magnet assemblies or rotor bodies is rigidly fixed to a rotor shaft and the other permanent magnet assembly or body is rotatable about the shaft relative thereto. Both are located in end to end relationship on a single axis.
By effecting relative rotation between the two rotor bodies, the output voltage of the generator may be varied as described more fully in such patents to achieve voltage regulation.
Those such systems should work well in theory. In practice, particularly in high speed generators as are utilized in aircraft generating systems, loading due to centrifugal force and other operational factors may render it difficult to achieve relatively precise angular adjustment of the movable permanent magnet rotor body with respect to the fixed permanent magnet rotor body unless a highly precise bearing arrangement is disposed between the two rotor bodies to support the shaft. Furthermore, because such prior art constructions utilize end to end rotors sometimes referred to as in-line rotors, the resulting generator package is relatively long and will create a large so called "overhung moment" when mounted in connection with an aircraft power plant in a cantilever fashion as is usual. This relatively large moment requires that the support for the generator be strengthened over what would be required for lesser overhung moment; and that inevitably leads to a weight increase which in turn decreases the useful load of the aircraft.
The present invention is directed to overcoming one or more of the above problems.